If the replacement pipeline is used, ARBfp is always on. Disabling it
can break shaders or the replacement pipeline, because the shader and
ffp code assumes the extension is on.
I don't like that I have to do this because the posFixup is in all
vertex programs, so its at the same position and could be loaded
globally. Unfortunately, there are only 256 env parameters usually,
which makes it impossible for any shader to use c256, even if it does
not use indirect addressing, and so we can't claim 256 constant
support.
I find it helpful for debugging to have this controlled at a central place,
without having to disable the entire GL extension or manually find all the
places where GL_SUPPORT(NV_VERTEX_PROGRAM2_OPTION) controls clipplane use. It
is useful for debugging the emulation code on NV cards and for debugging mac
driver issues.
b2f09fd204 accidentally got the
device->vs_clipping check wrong. The FFP replacement should emulate
clipping if GL can't do this natively with vertex shaders, not the
other way. Also don't emulate clipping if we're using fixed function
vertex processing because (a) clipping is always supported by GL in
this case, and (b), fragment.texcoord[7] is undefined. (Or in the
worst case set to something bad by the app).
If the needed constants are available, we can support all vs_2_0 and ps_2_0
requirements with the plain ARB extensions. We cannot however, run SM 2.0a or
SM 2.0b.
ps 1.x constants are clamped to [-1;1], constants in >= 2.0 pshaders
are not. This means we have to reload constants when switching between
those shader types in ARB. In GLSL this is not a concern because
constants are tied to program objects and are reloaded on a shader
change anyway.
This patch tries to find a free texture coordinate to load up to 4 clip
coordinates into the pixel shader, and uses KIL to throw away fragments
that are cut by a clipplane. If no free texture coordinate is found,
clipping is not done. If more than 4 clipplanes are used, only the first
4 are actually enabled. That should be pretty rare though.
Stefan Dösinger